Advanced Electro Deionization (EDI) technology is typically implemented downstream of Reverse Osmosis (RO) equipment and is used to produce High Purity and Ultra Pure Water.

As the successor to more traditional Ion Exchange resin systems, environmentally friendly EDI systems now set the standard for demineralized water production. Consuming only electricity, EDI equipment can operate continuously, making pure product water of consistent quality, without chemical waste. The systems have a very limited footprint and frequent maintenanceis not required.

What is EDI?

The Electro Deionization process uses ion exchange resins, ion-selective membranes and an applied DC electrical current to remove ions, such as salts, acids and bases. Weakly ionized materials, like dissolved silica, carbon dioxide, boron and some organics are also removed.

Most EDI modules are built with membranes that are permeable to either cations or anions, in an alternating sequence. The spaces between them act as liquid flow compartments, each with an inlet and an outlet. Dependent on the polarity of the ion exchange membrane and its orientation to a cathode or anode, an individual compartment either depletes the water of ions (product water) or accumulates ions (reject water).

To facilitate ion transfer in low ionic strength solutions, the dilute compartments and the concentrate compartments are filled with ion exchange resins. In an EDI module, a part of the feed flow, approximately 5% of the volume, continuously washes out the ions from the concentrate compartments. This concentrate outlet, also called the reject stream, is recirculated upstream of the RO system to be recovered, while the dilute compartments deliver purified product water.

Unlike traditional Ion Exchange resin systems, EDI needs no chemical regeneration. All EDI devices producing ultrapure water operate in electro-regeneration mode, in which the resins are continuously regenerated by H+ and OH- ions, released by the electrically-induced dissociation of water molecules.

EDI is a new type of desalination technology formed by organically combining electrodialysis technology and ion exchange technology. It can effectively remove all ions in the water, the resistivity of the effluent can be stabilized above 15MΩ.CM, continuous operation, no chemical pollution, high water utilization, and has broad application prospects in the preparation of high-purity water. The EDI device is applied after the reverse osmosis system to replace the traditional mixed ion exchange technology (MB-DI) to produce stable deionized water.

Most common uses for EDI

Demineralized feed water for (supercritical) high pressure boilers including for Concentrated Solar Plants

Pure water injection in gas turbines for NOx reduction

Ultra Pure Water for Microelectronics / Semiconductor fabrication

(Highly) Purified Water and Water For Injection for the pharmaceutical industry

Demineralized water for the petrochemical industry

Hospital applications including Hemodialysis

University and laboratory DI water

EDI technology has the following advantages:

Stable water quality

Easy to realize fully automatic control

No shutdown due to regeneration

No need for chemical regeneration

Low operating cost

Small plant area

No sewage discharge.

If you need to know more details about water treatment equipment, please contact me

Email-monica@zylabwater.com

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